Britney Spears kicked off her 'Piece of Me' Las Vegas residency last night (27.12.13).
According to MTV News, Britney powered through 23 huge hits over the 90-minute show, featuring costume changes, wigs and outrageous dancing.
Starting off the night with hit single 'Work B***h', the show was more of a nostalgic look back at her career, featuring older tracks like 'Gimme More'.
She was said to be singing live, her vocals shining past the backing track as some huge stars watched from the 9,000-strong audience.
Miley even joined in, getting close to a backing dancer when she was singled out of the crowd.
However, it was Mario who was brought up on stage to get involved in the show properly - and he was dressed in leather gear as he crawled across the stage on all fours.
The 'Extra' host was said to be a good sport, climbing up on stage when Britney singled him out in the crowd.
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